.\" Copyright 2016, IBM Corporation.
.\" Written by Mike Rapoport <rppt@linux.vnet.ibm.com>
.\" Copyright 2016, Michael Kerrisk <mtk.manpages@gmail.com>
.\" Copyright 2024, Alejandro Colomar <alx@kernel.org>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH UFFDIO_POISON 2const 2024-06-17 "Linux man-pages 6.9.1"
.SH NAME
UFFDIO_POISON
\-
mark an address range as "poisoned"
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.BR "#include <linux/userfaultfd.h>" "  /* Definition of " UFFD* " constants */"
.B #include <sys/ioctl.h>
.P
.BI "int ioctl(int " fd ", UFFDIO_POISON, ...);"
.P
.B #include <linux/userfaultfd.h>
.P
.fi
.EX
.B struct uffdio_poison {
.B "	struct uffdio_range  range;"
	                  /* Range to install poison PTE markers in */
.BR "	__u64   mode;" "     /* Flags controlling the behavior of poison */"
.BR "	__s64   updated;" "  /* Number of bytes poisoned, or negated error */"
.B };
.EE
.SH DESCRIPTION
Mark an address range as "poisoned".
Future accesses to these addresses will raise a
.B SIGBUS
signal.
Unlike
.B MADV_HWPOISON
this works by installing page table entries,
rather than "really" poisoning the underlying physical pages.
This means it only affects this particular address space.
.P
The following value may be bitwise ORed in
.I mode
to change the behavior of the
.B UFFDIO_POISON
operation:
.TP
.B UFFDIO_POISON_MODE_DONTWAKE
Do not wake up the thread that waits for page-fault resolution.
.P
The
.I updated
field is used by the kernel
to return the number of bytes that were actually poisoned,
or an error in the same manner as
.BR UFFDIO_COPY .
If the value returned in the
.I updated
field doesn't match the value that was specified in
.IR range.len ,
the operation fails with the error
.BR EAGAIN .
The
.I updated
field is output-only;
it is not read by the
.B UFFDIO_POISON
operation.
.SH RETURN VALUE
On success,
0 is returned.
In this case,
the entire area was poisoned.
.P
On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EAGAIN
The number of bytes mapped
(i.e., the value returned in the
.I updated
field)
does not equal the value that was specified in the
.I range.len
field.
.TP
.B EINVAL
Either
.I range.start
or
.I range.len
was not a multiple of the system page size; or
.I range.len
was zero; or the range specified was invalid.
.TP
.B EINVAL
An invalid bit was specified in the
.I mode
field.
.TP
.B EEXIST
One or more pages were already mapped in the given range.
.TP
.B ENOENT
The faulting process has changed its virtual memory layout simultaneously with
an outstanding
.B UFFDIO_POISON
operation.
.TP
.B ENOMEM
Allocating memory for page table entries failed.
.TP
.B ESRCH
The faulting process has exited at the time of a
.B UFFDIO_POISON
operation.
.SH STANDARDS
Linux.
.SH HISTORY
Linux 6.6.
.SH EXAMPLES
See
.BR userfaultfd (2).
.SH SEE ALSO
.BR ioctl (2),
.BR ioctl_userfaultfd (2),
.BR userfaultfd (2)
.P
.I linux.git/\:Documentation/\:admin\-guide/\:mm/\:userfaultfd.rst
